Holding power, adhesive strength and curved-surface peel resistance are some of the properties required of an adhesive. It has been widely recognized that the holding power and the adhesive strength of an adhesive are contradictory properties, as are the holding power and the curved-surface peel resistance. For example, increasing the holding power of an adhesive by increasing the amount of the crosslinking agent added to the adhesive to thereby increase the degree of crosslinking of the adhesive can lead to an increased molecular weight of the polymer component of the adhesive and can thus result in a decrease in the adhesive strength and the curved-surface adhesion resistance. On the other hand, decreasing the degree of crosslinking by decreasing the amount of the crosslinking agent added leads to a decreased molecular weight of the polymer component of the adhesive, resulting in an increased adhesiveness of the adhesive as well as in an increased adhesive strength thereof. This however decreases the heat resistance, holding power and curved-surface peel resistance of the adhesive.
An adhesive composition that exhibits the contradictory properties, i.e., holding power, adhesive strength and curved-surface peel resistance, in a well-balanced manner has been proposed (Patent Document 1). This adhesion composition is composed of a hard segment monomer whose homopolymer has a relatively high glass transition temperature (for example, 60° C. or above), a soft segment monomer whose homopolymer has a relatively low glass transition temperature (for example, −20° C. or below), a monomer whose homopolymer has an intermediate glass transition temperature, and a photoinitiator. Another type of adhesive composition has also been proposed that contains a monomer that can be homopolymerized to form a homopolymer with a glass transition temperature of −50° C. or below, an imide (meth)acrylate that is used in an amount of 1 to 20 parts by weight with respect to 100 parts by weight of the monomer, a photopolymerization initiator, and optional acrylic acid (Patent Document 2).    Patent Document 1: Japanese Patent Application Laid-Open No. 2000-073025    Patent Document 2: Japanese Patent Application Laid-Open No. 2002-285105